This invention relates to a control apparatus for controlling an operating parameter such as the ignition timing or the fuel injection timing of an internal combustion engine. More particularly but not exclusively, it relates to a control apparatus for an engine of an automobile.
In order to operate an internal combustion engine efficiently, it is necessary that fuel injection and fuel ignition in each cylinder take place with a prescribed timing. Therefore, engines are typically equipped with position sensors for sensing the position with respect to top dead center of each piston of the engine. A commonly used position sensor senses the rotation of a member, such as the camshaft of the engine, which rotates at one-half the rotational speed of the crankshaft and generates a corresponding output signal which indicates not only the rotational position of the crankshaft but also which piston of the engine is in a prescribed position. However, the camshaft is driven by the crankshaft through a mechanical transmission system comprising drive belts, timing chains, or the like. If slippage occurs in the mechanical transmission system, a phase difference can occur between the rotational position sensed by the position sensor and the actual rotational position of the crankshaft. Therefore, if the output signal of the position sensor is employed to control the engine timing, fuel injection and ignition may not take place with the proper timing, and optimal engine performance can not be obtained.